Well, as an amateur reader, I can speculate on some processes that might do that. Imagine a mass of crushed ice coming out of a valley, instead of a long tongue of intact ice being extruded and only breaking up at the tip.

I remember here at RC a few years ago someone (Mauri Pelto, perhaps?) the then thinking on this.

I’m going from memory here, someone please correct me if you can find his actual posts on the subject.

What I recall is someone telling us that the thinking at the time was that ice in the icecaps is plastic enough — flows slowly under pressure — that the ice sheets could not keep voids open internally through the wintertime, so the cracks and voids opening up during the summer through which meltwater could drain out wouldn’t persist. The ice would flow back together over the winter, once meltwater quit happening.

Perhaps this isn’t happening?

If glacial icecap retains holes from one season to the next, you can get air as well as water moving through the icecap.

I recall in the video Prokaryotes pointed us to, Alley says the old thinking on base temperatures for the icecap was it’d take ten thousand years for warming to penetrate down through the ice to reach the rock — and the new thinking is that with surface meltwater ponds and cracks carrying that water down to the rock layer, it takes ten minutes for warming to reach the rock base.

I was poking at all this stuff five or six years ago over at WMC’s site in his ‘Why do science in Antarctica’ thread. That was just about the time when the ‘ancient stable ice’ idea began to, er, show some cracks.

Hey, anyone here remember a 1950s idea that nuclear waste could be buried deep under the icecaps, where it would never go anywhere again? Now it’s starting to be clear that once pressure begins to be released the groundwater under an ice cap pushes back up and adds to the water flowing out under the ice. Hmmmm ….

http://onlinelibrary.wiley.com/doi/10.1111/j.1468-8123.2011.00355.x/full
“… Consolidation of glacial sediments that is less than expected from independent estimates of glacier thickness indicates that heads at the bases of past ice sheets were usually within 30% of the floatation value. This conclusion is reinforced by direct measurements of water pressure beneath portions of the West Antarctic ice sheet, which indicate average heads <7 m below floatation. Landforms of the Laurentide and Scandinavian ice sheets and recent observations in Greenland indicate that high seasonal discharges of surface water are conducted to the bed, despite thick ice at subfreezing temperatures. Therefore, in models of subglacial groundwater flow used to assess sites for nuclear waste repositories, a flux upper boundary condition based on water input from only basal melting will be far more uncertain than applying a hydraulic head at the upper boundary set equal to a large fraction of the floatation value."

I have now read the paper by Bamber & Aspinall, and these are my comments:

1. The study is based on a methodology for deriving subjective probability density functions (PDFs) by aggregating expert views. The methodology seems to be based on Cook (1991). They asked 26 experts to participate in the study and 13 experts answered the same questionnaire at two different times (2010 and 2012). Details about the methodology, including the list of the 13 participating experts are given in the Supplementary materials, which can be accessed free of charge here:http://www.nature.com/nclimate/journal/vaop/ncurrent/extref/nclimate1778-s1.pdf

I am not familiar with the methodology and cannot assess the validity. However, I do think that it provides an important alternative, and in many ways more transparent approach, to expert assessments compared to studies such as Pfeffer et al (2008) and Katsman et al (2011).

An important finding of the study is that the experts over the last two years showed a significant increased uncertainty over the contribution from WAIS to sea level rise during this century: “This indicates a growing view that a significant marine ice-sheet instability in the WAIS could initiate in the coming century.” (p 2).

Actually, each individual experts’ answers are provided in the supplementary materials. Looking at Supplementary Material Figure 7, one see that four experts changed their projections quite a lot. These experts now estimate upper limit of contribution from WAIS to be (30,20,15,10 mm/year in 2100), meaning “Upper and lower limits at the 95% confidence level, equivalent to the qualitative statement “virtually certain not to fall above/below these values””

I have not yet made my own calculation what this would mean for the total SLR projection, using the same method as in the paper. But given that the total SLR projection of +84 cm from ALL ice sheets (EAIS, WAIS, GrIS) for the aggregated upper bound is based on a total of 17.6 mm/yr in 2100, this number should be waaay much higher.

3. Another finding is the experts’ uncertainty of the underlying cause of the recent decades of accelerating mass loss of the ice sheets. It seems to be clear that much has to do with the ocean, but is caused by climate change or is it just a temporary phenomenon? The authors say that “Without a clearer understanding of the role and importance of internal variability in ice sheet-climate behaviour, predictions based on numerical modeling or extrapolation of observed changes are compromised” (pp 3-4).

This is yet another criticism of the reliability of present ice-sheet models to project decadal to centennial changes of mass loss from the ice sheets.

“Hey, anyone here remember a 1950s idea that nuclear waste could be buried deep under the icecaps, where it would never go anywhere again? Now it’s starting to be clear that once pressure begins to be released the groundwater under an ice cap pushes back up and adds to the water flowing out under the ice. Hmmmm ….”

I thought you might get a kick from the following link….if for some reason it doesn’t open correctly, I have an adobe version and would gladly email it to you.

Can we observe blocking patterns on the southern hemisphere, in regards to Australia’s heatwave (70% of continent affected)? What would be the Oscillation responsible, similar to the Jet Stream called? SAM? SOI?

You may remember that back in Q4 of 2012 I attempted to derive temperature projections for the AR5 RCPs, using methods described in Hansen et al.’s “Earth’s energy imbalance and implications”, i.e. Climate Response Functions and Green’s function. There’s been an interesting development in that story. At some point I happened onto the GFDL-CM3 page, which includes a graph showing RCP temperature projections (near the bottom of the page). The CM3 projections differed enough from mine to make me curious, so after failing utterly in my attempt to master the CM3 data interface, I contacted Larry Horowitz at GFDL. He kindly emailed me the corresponding data, so now I’m able to give more detailed results.

The RCP6 chart shows a near-perfect match between CM3 and the “intermediate” Climate Response Function. This makes it even more curious that the match is so poor for RCP4.5 and RCP8.5. Even if you ignore magnitude, the slope is obviously very different. I had assumed that this was because CM3 uses a different ECS. My projections used 3.0, but as Troy_CA brought to my attention (Nov. OT #123), according to Winton et al.’s 2012 Influence of Ocean and Atmosphere Components on Simulated Climate Sensitivities the ECS for GFDL CM3 is actually 4.6K. I can get a tolerable fit to RCP8.5 in the original CM3 graph by using ECS=4.0, as shown here, but this doesn’t make sense. How can it be that my ECS=3.0 projection fits CM3 so well for RCP6, but so poorly for RCP4.5 and RCP8.5?

[Response: Indeed. We ought to do a post on this. That we haven’t yet suggests not only that we’re all busy, but that there keep being records broken this year. It is almost getting boring. Look at the area of record-breaking drought, vs. that of record-breaking rainfall.–eric]

To me, it makes sense to look at record-breaking heat vs. record-breaking cold… but for drought and rainfall, it isn’t clear to me that it should be a “vs”, but rather an “and”. Eg, we expect to see increases in rainfall in some areas and decreases in others… so for temperature, the sign of climate change would be how much increase in heat exceeds increase in cold, but for precip, it should be the sum of the area in which drought and precip exceed historical norms.

Re: colorful met maps around current events in Australia, Stephan’s video, Impacts of Climate Change, posted here 20 December will seem prescient to anyone not familiar in fact, or principle, with its content:

“Human greenhouse gas emissions have continued to warm the planet over the past 16 years. However, a persistent myth has emerged in the mainstream media challenging this. Denial of this fact may have been the favorite climate contrarian myth of 2012, first invented by David Rose at The Mail on Sunday with an assist from Georgia Tech’s Judith Curry, both of whom later doubled-down on the myth after we debunked it. Despite these repeated debunkings, the myth spread throughout the media in various opinion editorials and stunts throughout 2012. The latest incarnations include this article at the Daily Mail, and a misleadingly headlined piece at the Telegraph.

As a simple illustration of where the myth goes wrong, the following video clarifies how the interplay of natural and human factors have affected the short-term temperature trends, and demonstrates that underneath the short-term noise, the long-term human-caused global warming trend remains as strong as ever…”

It was for those very reasons I came looking for advice. I was looking for as an arbitrarily neutral investigation as possible. Just the correct methodology and then see what happens. So far, I’ve found that it’s warmed here in the last 30 years but not as much as the globe.

I’m currently parsing the temperature data for TYS since that data goes back over a hundred years. Later I’ll look at precip and some other fields.

Some good stuff on just which records have been set (highest national mean, numerous local records, longest stretch with highs above 39C, but not the highest station reading ever) and on potential effects. (Not to mention sociopolitical context.)

I’ve started a series on Visualizing Atmospheric Radiation, with a line by line model written in Matlab that uses HITRAN and the water vapor continuum from Pierrehumbert’s 2010 book. Some quick notes on the model assumptions and limitations in one of the comments.

I looked into whether the Voigt profile is needed given that so far the model goes up to about 50 hPa.

I’d appreciate technical comment on whether my assumptions and results are correct. I’m hoping to avoid using the Voigt profile for obvious reasons.

Then I can produce some results showing how TOA balance is changed with various concentrations of CO2 and why. Plus lots of other interesting stuff.

Thanks.

PS Pierrehumbert’s book is well worth reading (even though I have only read about 1/3 of it so far). He briefly stopped by the Science of Doom blog a while ago on his book tour and that’s why I ended up buying it..

Glum reading dept.: U.S. National Climate Assessment Federal Advisory Committee’s Draft Climate Assessment Report Released for Public Review. At a mere 1193 pages it’s average by federal standards. So far it seems mostly right on to me, though I notice that while it attributes 20% of current emissions to the U.S., discussion of our share of historical emissions and is notably absent.

Hank: “That was the usual bogosity being reported as though it’s news”. If you’re referring to your link to The Australian, it’s paywalled. I suppose that’s a good thing if the news is bogus; IMHO, truthful news should be free, but people who want to read bogus climate news should have to pay for it.

Susan @95: Thanks for the tip! I’ve been following the Erlichs for what seems like forever and I’m glad they’re still with us. This might be the best meta-analysis I’ve seen yet. A couple of paragraphs really stood out for me.

Unfortunately, essential steps such as curbing global emissions to peak by 2020 and reducing them to half of present levels by 2050 [66] are extremely problematic economically and politically. Fossil fuel companies would have to leave most of their proven reserves in the ground, thus destroying much of the industry’s economic value [67]. Because the ethics of some businesses include knowingly continuing lethal but profitable activities [68], it is hardly surprising that interests with large financial stakes in fossil fuel burning have launched a gigantic and largely successful disinformation campaign in the USA to confuse people about climate disruption [69,70] and block attempts to deal with it [71].

I’ve been thinking/saying something like this for a while now. It’s time to confront ethics, or the absence of them. “A society that values accumulation of wealth above all else isn’t a society at all, it’s a corporation.” (from me not Erlich).

There are great social and psychological barriers in growthmanic cultures to even considering [population reduction]. This is especially true because of the ‘endarkenment’—a rapidly growing movement towards religious orthodoxies that reject enlightenment values such as freedom of thought, democracy, separation of church and state, and basing beliefs and actions on empirical evidence. They are manifest in dangerous trends such as climate denial, failure to act on the loss of biodiversity and opposition to condoms (for AIDS control) as well as other forms of contraception [122]. If ever there was a time for evidence-based (as opposed to faith-based) risk reduction strategies [123], it is now.

The endarkenment! The opposite of an enlightenment. I had never heard this term before but it turns out to have a long history going back to the Reign of Terror. “Growthmanic” is excellent too.

Serious global environmental problems can only be solved and a collapse avoided with an unprecedented level of international cooperation [122]. Regardless of one’s estimate of civilization’s potential longevity, the time to start restructuring the international system is right now. If people do not do that, nature will restructure civilization for us.

This is classic Erlich! It’s almost a punchline, and makes me think of Oscar Wilde’s “If you want to tell people the truth, make them laugh…” But my favorite quote is this last one, which could be right out of Kaczynski’s “Industrial Society and its Future”:

The industrial revolution set civilization on the road to collapse, spurring population growth, which contributed slightly more than overconsumption to environmental degradation [136]. Now population combined with affluence growth may finish the job.

I wonder given all the fuss about the Met Offices latest Decadal projections if anyone has got the raw data and has created yearly averages based on the ensemble averages.

IE 2013 = 0.49 C; 2014 = 0.52 C; etc.

Some people are making lots of fuss that the data “confirms” warming has “stopped”. That is very disengenous and being able to state what the yearly averages are going out – with an underlying upward trend – would be helpful, especially as these can then be compared with 1998 etc.

I can’t find the raw data to do this – anyone any ideas if it’s been published, or have the Met Office only published the graphs and not the underlying data?

http://vimeo.com/55073825
“… a short film documenting astronauts’ life-changing stories of seeing the Earth from the outside – a perspective-altering experience often described as the Overview Effect…. first described by author Frank White in 1987 ….”